Frequency-meter.



P. GORDON.` FREQUENCY METER.

APPLICATION FILED APR. I3, 1914- Patented May 4, 1915.

l messes Z5/venan i -UNITED STATES PATENT GFFICE.

PHILIP GORDON, 0F BARRE, VERMONT, ASSIGNOR 0F ONE-HALF T0 ADELAIDE ESTEE,

0F 'MONTPELIER, VERMONT.

FREQUENCY-METER.

To all whom.- it may concern:

Be it known that I, PHILIP GORDON, a citizen of the United States, residing at Barre, in the county of Washington, State of Vermont, have invented a rcertain new and useful Improvement in Frequency-Meters, of which the following is a specification, reference being had therein to the accompanying drawings.

This invention relates to measuring instruments but more particularly to such as are adapted for determining the frequency of Vibrations and has for its object to provide means for doing mechanically what has heretofore been accomplished only by human skill.

In the present embodiment the invention has been treated in connection with a mehanism for the tuning of a piano, but it should be clearly understood that it is not limited to such application as it is adaptable for use in measuring sound, light, electric or f practically any other form of vibrations as will be readily understood from the following detailed description.

In tuning a piano heretofore, the tuner has depended upon the acuteness of his ear to determine the pitch of the strings so that only a fair degree of accuracy could be obtained, depending entirely upon his keenness of ear and experience and knowledge of the art. The difference in pitch between one note and another is determined by the frequency of the beats produced when these notes are sounded simultaneously and is directly proportioned thereto. It is usually customary for a tuner to tune one string of one note to a standard pitch and then to tune one string of each other note in the instrument from this one. When there is more than one string for a note, the other string or strings are tuned to the one first tuned for the same note. If the frequency of these beats was easy .to determine, the problem of tuning a piano would be comparatively simple, but such is not the case particularly on account of the over-tones and combination tones which beat in relation to each other. The ear therefore has to first determine which is the proper beat to count.

The ratios of harmony in music are purely mathematical and can be determined without any musical ear or knowledge of music. y

Each note has a-defnite mathematical relation to every other note 1n the piano. The

Specification of Letters Patent. y

Patented May 4, 1915.

frequency of each note has therefore a certain denite relation to a given note which has an assigned frequency as for example, note middle (a) has av frequency of four hundred and thirty-five vibrations per second international pitch and every other note has a definite mathematical relation to this note.

In the present invention means are provlded for measuring mechanically the vibration frequency of a string so that the strings may be properly tuned by a person having no musical ear or v knowledge of music.

The operationV of the device is based on the principle of relative or absolute synchronism between a device rotating at a predetermined'speed and a wire vibrating at the same speed or a multiple thereof. Numerous mechanical means might be adopted forwso indicating this synchronism but as these are well known to those skilled in the art, only one structure will be described hereinafter,

though it should be clearly understood that the invention is not limited to this particular embodiment.

The many other features and advantages of 'the invention will be fully described hereinafter and included in the claims.

One embodiment of the invention is shown in the drawings in which the figure is a diagrammatical view of the invention complete.

Referring to the drawings the invention is shown to comprise an electric motor 10 upon the main shaft of which is mounted an inter-l ferometer disk 11 having one or more perforations 12 arranged at `an equal distance from its axis of rotation. The speed of this motor is regulated by a rheostat 18 which will be described more fully hereinafter. Power is. conducted to this rheostat from a source of power supply M through the switch 15. To the switch' 15 is also connected a circuit 16 which operates a light 17 which is preferably inclosed in a substantially tubular member 18 in which is a concentrating lens 19 and a rectifying lens 20 to cause the light to be projected from the tubular member in a single concentrated ray. The rectifying lens 20 is preferably located at the focal point of the lens 19.

A microphone 21 is arranged to be placed opposite or adjacent to the string 22 of the piano which is the one desired to be tuned,

and this microphone canthen be placed in with the suspensory.

A second circuit 30 is connected to the posts 31 and 32 of the oscilliograph 27 which are in turn connected to the magnetizing coils 33 and 34 of the oscilliograph. As this cscilliograph is a well known structure, itis not deemed necessary here to describe its construction as this Will be readily evident to one skilled in the art.

The ray of light issuing from the tubular member 18 strikes upon the face of the mirror 29 and is here reflected thereby upon the prism 35 and refracted upon the screen member 36 preferably a piece of ground lass. This screen is here placed in rear o the interferometer disk 11 through it may be placed in front thereof or omitted entirely.

The sound waves produced by the vibrations of the string 22 will cause a corresponding intermittent flux in the circuit 22 which` will be intensified by the induction coil 24, causing the mirror 29 to` oscillate and the beam of light 37 to swing backward and forward through a upon being reflected by the prism 35 in the manner described will move toward and from the axis of rotation of the disk 11.

The rheostat is provided with positions corresponding to the thirteen notes of an octave, position 1 being C; position l2, Cit; 3, D; 4, Dit; 5, E; 6, F; 7, Ft; 8, G; 9, Git; 10, A; 11 Ait; 12, B; and 13, C. In the drawing the operating arm 38 is set in position 3 which would therefore correspond to the pitch D which is assumed to be the desired pitch of the string 22. The switch 15 is now thrown in, causing the motor 10 to operate. It is essential that the motor be so constructed and adjusted that each of the positions on the rheostat will produce a definite number of revolutions per minute of the motor. In the present embodiment position 1 should give 1920 revolutions per minute or 32 revolutions per second; posi tion 2, 2160 revolutions per minute or 36 revolutions per second; position 3, 2400 revolutions per minute or 40-per second; position 4, 2700 revolutions per minute or 45 per second; and so on for the other positions, the rate of each being determined by. the

corresponding number of vibrations neces-l sary to produce the note indicated for such position. The motor here shown is of the direct current type provided with differ' ential winding compounded to take care of coil-22 at the rate of small angle which variations of temperature and current sup ply. In the circuit connecting the rheostat with the' source of supply 14 is preferably placed a line voltmeter 39.

In commercial work it is possible to obtain sufficient accuracy of revolution of the motor to Permit of securing a very accurate tuning o the strings of the piano. The device is also readily applicable for use in scientific tests where an exact reading of the revolutions of the motor would be necessary. To provide for such a case, the device may be provided with a ma eto tachometer 40 which could be driven om the main shaft of the motor by a belt 41 or by any other suitable means. Connected with this tachometer is a recorder 42 which would be gaged in revolutions per minute.

aving now started the motor 10 in the manner described with the rheostat arm in position 3, the string 22 is struck to produce the note. The sound waves enter the microphone 21, causing an electric vibration in the 40 per second. The mirror 29 is-thus caused to oscillate at a corresponding rate which will produce a like oscillation of the ray of light 37 which strikes the ground lass plate 36 in the manner described. If t e ray of light is oscillating at the same frequency as the disk 11 is revolving or a multiple thereof on the ground glass plate 36, the light will show through the apertures 12 as the two will be operating in synchronism, but if the two are not operatin at the same frequency or a multiple thereo the light will not show. The tuner will then adjust the string 22 and continue to strike the'same until the light does appear which will indicate that the string is vibrating at the rate of 40 vibrations per second or -a multiple thereof depending on the octave desired and therefore is at the proper pitch to produce the note D. Each of the other strings in the octave is tuned in similar manner by setting the rheostat arm at the proper position.

If the device is to be used to determine other than sound vibrations the only difference in the device would be that different receiving means would be used in place of the microphone, the. nature depending on the type of vibrations to be measured, as will be readily understood by anyone skilled in the art.

What I claim as my invention to secure by Letters Patent is and desire In a device of the class described, a A

described, a capable of beatl a. plurality of different A lmown'speed, and means for indicating -v .rality of different known whether the vibrating member is vibrating at a higher or lower number of vibrations in a period of time than the revolving member is making revolutions in the same period of time. Y

4. In a device of the class described, a revoluble member, means for operating said member at a plurality of diilerent known speeds, a vibrating element, and means for indicating when the vibrating element is vibrating at the same rate that the revolving member is revolving in each'of its different speeds. j

5. In a device of the classjdesci'ibed, a revoluble member, means for operating said member through a certain -range of known speeds, a vibrating element, and means for indicating when the vibrating element is vibratin at any multiple of the rate that the revoving member is revolving at any of the s eeds in such range. t

6. Ina device of the class described a member capable of'be'ing revolved ata p uds, a vibrating element, means for indicating the vibrations of such element, and means for comparing the rate of vibration of the vibrating ele' ment 4with the rate of revolutions of the re-v volving member.

7. In a device of the class described, a revoluble member', `means for operating said revoluble member, means for controlling said operating means to cause said member tobe driven at any one of a plurality of diii'erent fixed speeds, a vibrating element means for indicating the vibrations of sai 'vibrating element, and means for instantly determinin when the rate of vibration of said vibrating element is the same as the rate of revolution of the .revoluble element at an one of its rates of speed.

8.. n a device of the class described, a revoluble member, means for operating said revoluble member, means for controlling said operating meansto cause said member -to be driven at any one of a plurality of vdiiererit fixed speeds, a vibrating element, indicating means adapted to show the vibrations of the vibrating element, and means for determining from said indicating means revoluble member.

and said revoluble means when the vibrating element and the revoluble member are operatin in synchronism at each of the speeds o the revoluble member. v

9. In a device of the class described, a revoluble disk, means for operatingv said disk by power, a controller adapted to cause said operating means to rotate said disk at any desired o'neo a plurality of different fixed speeds, a vibrating element, electrically operated means for indicating the vibrations of said vibrating element, and means for comparing the rate of revolution of said revoluble member at each of its diierent speeds with e rate of vibration of the vibrating element asshown by said indicating means. I

' 10. In a device of the class described, a revoluble member, means for revolving said member at a predetermined rate, an electric circuit, means for producing electric vibrations in such circuit, means for indicating the vibrations in said circuit, and means for comparing the rate :of vibration inI suchcircuit with the rate of revolution of such 11. In 'a device of the class described, a revoluble member, means for revolving said member at any one of a known range of speeds, an electric circuit, means for producing electric vibrations in such circuit, means for indicating the vibrations in said circuit, and means for comparing the rate of vibration in such circuit with the rate of revolution of such revoluble member for ldetermining when such vibrations occur with the same frequency as the revolutions of the revoluble member at each speed of said member.

12. In a device of theiclass described, a

revoluble member, means for revolving said member at any one of a known range of speeds, a vibrating element, an electric circuit, means for producing periodic electric vibrations in said circuit of the same freuency as the vibrations of said vibrating e ement, means for indicatin the vibrations in such circuit, and means or determining when the frequenc of such vibration is the same as the revo utions of said revoluble member at any of its speeds.

In testimony whereof I airix my signature in the presence of two witnesses. v

PHILIP GORDON. Witnesses:

-HARTLEY W. BAirrm'i'r', HANNAH M. KENNEDY. 

